CHEM 297 INTERMEDIATE CHEMISTRY II LABORATORY - DOC

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					                        CHEM 297 INTERMEDIATE CHEMISTRY II LABORATORY
                                   WEEKS OF FEBRUARY 21 AND 28
                          INORGANIC COMPLEX SYNTHESIS AND ANALYSIS

                          POTASSIUM BIS-OXALATOCUPRATE (II) DIHYDRATE
                                         K2[Cu(C2O4)2].2H2O

SYNTHETIC PROCEDURE

                CuSO4.5H2O + 2K2C2O4.H2O  K2[Cu(C2O4)2].2H2O + K2SO4 + 5H2O

A solution of 4.17 g of copper (II) sulfate pentahydrate dissolved in 9 mL of water is heated to 90 oC and is added
rapidly to and with vigorous stirring to a solution of 12.3 g of potassium oxalate monohydrate in 35 mL of water,
which is also at 90oC. The solution is then cooled to 10oC in an ice-bath and the resulting precipitate is filtered,
washed rapidly with 9 mL of cold water, and dried in an oven at 50 oC for 12 hours.

ANALYSIS

1. Cu by electrodeposition
Take a sample of the compound in the range of 0.0300 g, weighed accurately, and place it in a tall form beaker. Do
all the following in the fume hood. Dissolve the sample in 1 or 2 mL of concentrated H 2SO4. Heat the mixture on a
hot plate until the fumes of SO3 are just detected. CAUTION: H2SO4 is a very strong acid. SO3 fumes should not
be inhaled. Let the mixture cool and then add with extreme caution 5 mL of concentrated HNO 3. This step is
potentially dangerous so take adequate precautions against spattering or spilling. Evaporate the mixture slowly to
dryness and avoid charring the organic material that may remain. Do all the above in the hood.

Treat the residue with a mixture of 5 Ml 6M H2SO4 and 3 mL 6M HNO3 and dilute to 100 mL total volume
(volumetric flask with water). Add about 0.5 g urea to the solution and electrolyze using platinum electrodes (see
below for caring of electrodes) at a setting of 2 volts for a period of 30 - 45 minutes. Check for complete deposition
on a portion of the solution by addition of excess NH4OH. Wash the electrodes with water, then acetone, and dry
for 1 minute at 100oC, cool in a dessicator and weigh. Clean the electrodes (see below).

Care of platinum electrodes
1. Use 6M HNO3 to clean the electrodes, then wash with water.
2. After the electrodes are clean, dry in an oven and cool before weighing. After cleaning and drying handle the
    electrodes with a strip of paper to keep grease and dirt off the surface.
3. Never carry out electrolysis or cleaning in solutions containing Cl- ions.

2. Organic ligand
Obtain the IR spectra of your complex. Assign the major absorptions in the spectrum to the appropriate bond
vibrations.

				
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